Climate change after tropical deforestation: seasonal variability of surface albedo and its effects on precipitation change

摘要

This work studies the seasonal effects of the surface albedo change after a tropical deforestation and its influence on the seasonal pattern of precipitation in Amazonia. Results of the climate simulation study of Costa and Foley are used to represent the precipitation changes in a scenario where all tropical forest was replaced by pasture. The simulated forest and pasture albedo are compared to both the forest and pasture albedos observed during the Anglo-Brazilian Amazonian Climate Observation Study (ABRACOS) project. The surface albedo measurements provided verification that both forest and pasture albedo show seasonal variability, with the forest albedos higher in the dry period (June-November) and lower values in the rainy period (December-May), while the pasture albedo decreases in the dry season. Most of the characteristics of the observed differences in albedo are present in the simulated albedo too, which is in part due to the ability of the land surface parameterization to represent vegetation phenology. Verification was also obtained to show that the seasonal variability in the reflected radiation anomalies, caused by the tropical deforestation, is associated with seasonal fluctuations in the precipitation anomalies. This study demonstrates that most of the spatial and seasonal variability in the simulated climate after a tropical deforestation can be explained by the difference in the radiation reflected by the surface.